Switch latches according to the generic type are known, e.g., from German Patent No. 42 27 213 A1. The content of German Patent No. 42 27 213 will be incorporated into the present application. German Patent No. 42 27 213 A1 describes a switch latch which opens in a reliable way, and which switch latch presents advantages for manufacture that are brought about by a corresponding design. A system which includes a switching gate, toggle levers, and latch spring can especially form a simple but effective snap-action contact system. In low-voltage switching devices, it is often advantageous to aim at improved switching properties by increasing the contact force exerted between the contact pieces. But this is made difficult by the limited amount of force available from the switch latch.
The change-over point, at which change-over point the switch latch is switched on, and which change-over point is determined by the latch spring that exerts a force upon the support of the toggle levers at the supporting lever, has also been found to scatter even beyond the desired range under the effect of friction and manufacturing tolerances in switch latches of a design that is known, e.g., from German Patent No. 42 27 213 A1. The spring pretension of the latch spring may not be sufficient to achieve a full switching operation for the switching shaft and for the contacts when the change-over point scatters in the direction of "too early."
In other words, the latch spring exerts a force upon the support of the toggle levers. This force determines the change-over point at which change-over point the switch latch is switched on. This change-over point ideally occurs at some point in a pre-determined range. Due to friction and manufacturing tolerances in known switch latches, the change-over point has been found to scatter and move to a point outside of the desired pre-determined range. When the change-over point occurs "too early", i.e. at a point before the pre-determined range, the spring pretension of the latch spring may not be sufficient to achieve a full switching for the switch shaft and, consequently, for the contacts.
In turn, this may cause faulty contacting within the switching device itself and thus lead to erratic electrical behavior of the systems connected to it. The excessive scattering of the change-over point makes the temporal and logical coordination of the control points for auxiliary equipment more difficult since the operation of auxiliary equipment, e.g., of auxiliary switches, also depends on the position of the toggle lever of the switch latch.
When the switch latch is closed too slowly, friction may prevent the switch latch from developing the dynamic energy which is required to close the contacts completely. This also leads to errors in the electric behavior of the system.